Metal and metalloid bioconcentration capacity of two tropical bivalves for monitoring the impact of land-based mining activities in the New Caledonia lagoon

The clam Gafrarium tumidum and the oyster Isognomon isognomon have been proposed as potential biomonitor species of metal contamination in the New Caledonia lagoon. The influence of dissolved concentrations of As, Cd, Co, Cr, Mn, and Zn on uptake and depuration kinetics, tissue and subcellular distribution of these elements was investigated in both species. Results indicate that both bivalves take up elements proportionally to the dissolved concentration for Cd, Cr and Mn in the surrounding water over the entire range of concentrations tested (three orders of magnitude), and up to the second and third highest added metal concentration tested for Co (23 ng l−1) and Zn (700 ng l−1), respectively. All elements were efficiently retained in bivalve tissues (estimated Tb1/2 ranging from 16 d to ∞), suggesting that both species should be able to preserve a record of contamination events over a long period of time. Considering the specific range of concentrations examined here, G. tumidum and I. isognomon would therefore serve as adequate biomonitor species to monitor dissolved metal contamination in the New Caledonia lagoon waters.